This application proposes to expand upon the findings of the DASH study, which showed that a dietary pattern emphasizing fruits, vegetables and low fat dairy products and is overall reduced in total and saturated fat significantly lowers blood pressure (BP). The DASH diet is particularly effective in African Americans and in individuals with systolic hypertension. However, we do not know if the DASH diet affects the pathophysiology of the hypertensive process. Our preliminary data support the possibility that the DASH diet interrupts the renin-angiotensin system. This raises the intriguing possibility that the DASH diet will favorably impact on cardiovascular and renal hemodynamics in patients with isolated systolic hypertension. Therefore, the central hypothesis of this application is that the DASH diet affects central aortic stiffness, diastolic relaxation and renal and vascular reactivity to angiotensin II (Ang II) by lowering tissue renin-angiotensin system activity. We will test this hypothesis in patients with isolated systolic hypertension, by determining if the DASH diet (1) reduces central aortic stiffness, as measured by characteristic impedance (Zc) and carotid-femoral pulse wave velocity (CF-PWV), (2) improves diastolic relaxation, as measured by early diastolic myocardial velocities (Ea), (3) vasodilates renal blood flow and enhances the renal and vascular response to Ang II, and (4) affects these hemodynamic parameters in a manner that is similar to ACE inhibition. We will study 55 participants with isolated systolic hypertension in a randomized, cross-over feeding study of the DASH diet and a control diet. Participants will enter a 2- week run-in period on the control diet followed by two 6-week feeding periods eating the control diet or the DASH diet in random order. After each feeding period, conduit vessel hemodynamic measurements, diastolic relaxation and renal and vascular responses to Ang II will be measured before and after captopril administration. Findings from these studies will determine if the DASH diet favorably affects mechanisms that are altered by the hypertensive process, including renal and cardiac performance, in a group of individuals at higher cardiovascular risk.